Turbocharged and supercharged engines may be configured to compress ambient air entering the engine in order to increase power. Compression of the air may cause an increase in air temperature, thus, a charge air cooler may be utilized to cool the heated air, thereby increasing its density and further increasing the potential power of the engine. Ambient air from outside the vehicle travels across the charge air cooler to cool intake air passing through the inside of the charge air cooler. Condensate may form in the charge air cooler when the ambient air temperature decreases, or during humid or rainy weather conditions, where the intake air is cooled below the water dew point. Condensate may collect at the bottom of the charge air cooler, or in the internal passages, and cooling turbulators. When torque is increased, such as during acceleration, increased mass air flow may strip the condensate from the charge air cooler, drawing it into the engine and increasing the likelihood of engine misfire.
Other attempts to address engine misfire due to condensate ingestion involve avoiding condensate build-up. However, the inventors herein have recognized potential issues with such methods. Specifically, while some methods may reduce or slow condensate formation in the charge air cooler, condensate may still build up over time. If this build-up cannot be stopped, ingestion of the condensate during acceleration may cause engine misfire. Another method to prevent engine misfire due to condensate ingestion includes trapping and/or draining the condensate from the charge air cooler. While this may reduce condensate levels in the charge air cooler, condensate is moved to an alternate location or reservoir, which may be subject to other condensate problems such as freezing and corrosion.
In one example, the issues described above may be addressed by a method for a charge air cooler. The method comprises, responsive to a condensate level in the charge air cooler, increasing boost pressure and maintaining a requested level of torque by routing a portion of air flow exiting the charge air cooler to an intake passage upstream of a compressor.
In this way, a charge air cooler clean-out cycle may periodically purge the condensate from the charge air cooler. The charge air cooler clean-out cycle may be initiated in response to a condensate level in the charge air cooler, which may be estimated based on mass air flow in one example. By increasing air flow through the charge air cooler, controlled amounts of condensate may be blown off into the engine without causing misfire. The increase in air flow through the charge air cooler and resultant torque disturbance that may occur if the air flow were to reach the engine, may be counteracted by routing a portion of the air from the charge air cooler back to the intake passage upstream of the compressor. In this way, the clean-out cycle may not alert the vehicle operator. By performing this clean-out routine, condensate levels in the charge air cooler may be maintained at a low level to prevent engine misfire during normal vehicle operation.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.